1. Field of the Invention
The field of the invention is energy monitoring devices such as watt meters and watt-hour meters, and more specifically, power transducers used instead of utility power meters to provide inputs to energy demand/schedule controllers. 2. Description of the Prior Art
Watts transducers are disclosed in Martin et al, U.S. Pat. No. 3,794,917, issued Feb. 26, 1974, and Callan, U.S. Pat. No. 4,079,313, issued Mar. 14, 1978. Watts transducers generate a voltage proportional to the instantaneous power (watts) being consumed by a load. In U.S. Pat. No. 4,079,313, this voltage is converted to pulses which are counted to monitor total energy demand in watt-hours. In Milkovic, U.S. Pat. No. 3,976,941, issued Aug. 24, 1976, a circuit that generates a voltage proportional to single-phase instantaneous power (in watts) is included in an electronic watt-hour meter.
Energy demand/schedule controllers require an input signal proportional to the watt-hours supplied to the building or facility being served. This signal is sometimes available from the utility company's power metering equipment, which provides contact closures, or "pulses," where each pulse represents a unit of energy consumption, such as a watt-hour. When power meter contacts are not available, a watt-hour transducer, such as disclosed in U.S. Pat. No. 4,079,313, cited above, can be used to monitor energy consumption. Where the power factor and voltage in a power distribution system are relatively constant, an amp-hour transducer is sometimes used to generate pulses for an electrical demand controller.
The transducers described above are limited to monitoring a single polyphase supply line carrying power to a load within a building or facility.